Central Nervous System

Brain Stem

• Oldest region of brain we know of

• Autonomic function

• basic vegetative functions

• No conscience thinking

• Ex: heart rate, respiration, etc.

Medulla

• origin of vagus nerves

• Motor nerve tracks cross over

• respiration, heart rate, sneezing swallowing

Pons

• Sleep, respiration, swallowing, hearing, taste, posture, eye movement

Midbrain

• Relay center

Thalamus and Hypothalamus

Big relay center for brain function— endocrine tissues, cerebral cortex, etc. Lots of pathways in the brain

• Consist of many nuclei— cluster of cell bodies that have a similar function

• Thalamus— relays sensory signals, including motor signals, to the cerebral cortex, and the regulation of consciousness, sleep, and alertness

• Hypothalamus— endocrine regulator, ANS regulator, many functions

Pituitary and Pineal gland

• Regulated by hypothalamus

• Pituitary (described in detail in the endocrinology lecture)

  • Releases many hormones

• Pineal gland

  • Releases melatonin

Melatonin— produced in the absence of light, retinal signals to hypothalamus, and activates pineal gland

Cerebellum

• “Little brain”

• Sorts and processes signals to maintain balance, posture, and carry out our coordinated movement

• Largest relative part of the bird brain (flight)

• Reticular formation

Limbic system

• Several structures

• Reacts to odors

• Emotions

• Memories

• Arousal

Cerebral cortex

Most recently evolved part of the brain, outermost 6 layers of neurons

• Higher brain function, cognition, acquiring knowledge, complex thought, and complex behavior.

• Central sulcus— divides into front and back

  • Primary somatosensory cortex— caudal to central sulcus, neurons firing tells animal a specific body region is being stimulates

  • Primary motor cortex— rostral to central sulcus, neurons firing tell skeletal muscles to move

Premotor Cortex and Supplementary Motor Area

• Rostral to primary motor cortex

• Premotor cortex (PMC)— conscious feedback

• Supplementary Motor Area (Supp MA)— coordinate via past experiences and learned responses

Autonomic Nervous system

Parasympathetic Division

• Keeps body energy use low

• Animal after eating:

  • BP, HR, + respiratory rates are low

  • Gastrointestinal tract activity is high

  • The skin is warm and the pupils are constricted

• Outflow:

  • Few cranial nerves

  • most carried by vagus nerve

  • some sacral nerves

  • NT: mostly ACh

Sympathetic Division

• Fight or flight

• Promotes adjustement during exercise

• Thoracic and lumbar regions

• Ganglia— collection of soma in the PNS

• NT at target organ: mostly epinephrine and norepinephrine

ANS Receptors

• Cholinergic— bind ACh

  • Muscarinic— stimulatory and inhibitory

  • Nicotinic— always stimulatory

• Adrenergic

  • Alpha and Beta— two or three subclasses

  • Effects of norepinephrine binding to:

    • Alpha receptors is generally stimulatory

    • Beta receptors is generally inhibitory

Activation of Smooth Muscle

• Sympathetic axon at artery wall

• NE, ATP, neuropeptide Y (NPY)

• ATP binds receptor

  • Opens calcium and sodium channel

  • Depolarizes→ opens calcium channel→ contraction

• NE binds receptor

  • G-protien coupled receptor→ calcium channel opens→ contraction

Deactivation of Smooth Muscle

• Parasympathetic axon at artery wall

• ACh, Nitrous oxide, and vasoactive intestinal peptide

• ACh binds receptro on blood vessel→ g-protein coupled receptor→ increase intracellular calcium→ produce and release NO

• NO binds in smooth muscle cell→ relaxation

• VIP binds receptor→ ???→ relaxation